This paper provides a new contribution to the simplified analytical treatment of collisions between two ships. It is directly connected to the well-known super-elements method, which is a simplified procedure allowing for a quick estimation of the damages caused to both the striking and struck vessels during such events. In this article, a new analytical formulation is presented for estimating the impact resistance provided by inclined ship side panels. Two different scenarios are treated. We first deal with the case of an impact between the oblique plate and the stem of the striking ship, and then we consider the situation where the inclined panel is impacted by the bulb. For these two scenarios, an analytical formulation relating the force and the penetration is provided and these developments are validated by comparing them to the results of finite elements simulations. Finally, the new inclined plate super-element is integrated in a simplified model of a frigate collided by another ship, and the resistance given by the super-elements method is then compared to the one obtained by a numerical simulation of this collision.